A jar contains $10$ red balls, $7$ green balls, and $8$ blue balls. If a ball is randomly chosen, what is the probability that it is not blue?
There are $10 + 7 + 8 = 25$ balls in the jar. There are $8$ blue balls. That means $25 - 8 = 17$ are not blue. The probability is $ \frac{17}{25}$.